Methods of dry stripping boron-carbon films

ABSTRACT

Embodiments of the invention generally relate to methods of dry stripping boron-carbon films. In one embodiment, alternating plasmas of hydrogen and oxygen are used to remove a boron-carbon film. In another embodiment, co-flowed oxygen and hydrogen plasma is used to remove a boron-carbon containing film. A nitrous oxide plasma may be used in addition to or as an alternative to either of the above oxygen plasmas. In another embodiment, a plasma generated from water vapor is used to remove a boron-carbon film. The boron-carbon removal processes may also include an optional polymer removal process prior to removal of the boron-carbon films. The polymer removal process includes exposing the boron-carbon film to NF 3  to remove from the surface of the boron-carbon film any carbon-based polymers generated during a substrate etching process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 61/485,534, filed May 12, 2011, which is herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to methods of drystripping boron-carbon films.

2. Description of the Related Art

Boron-carbon films, such as boron-doped carbon, have demonstratedsuperior patterning performance as compared to amorphous carbon whenbeing used as an etching hardmask. However, boron-carbon films are noteasily stripped, since boron-carbon films cannot be ashed using anoxygen plasma. Boron carbon films can be dry stripped using fluorine orchlorine along with oxygen; however, fluorine and chlorine are corrosiveto dielectric materials such as silicon oxide, silicon nitride, andsilicon oxynitride commonly found on semiconductor substrates. A wetetch solution containing sulfuric acid and hydrogen peroxide can alsoremove the boron-carbon films; however, the wet etch solution can damageexposed metal surfaces or embedded metals also commonly found onsemiconductor substrates.

Therefore, there is a need for an improved method of removingboron-carbon films from substrates.

SUMMARY OF THE INVENTION

Embodiments of the invention generally relate to methods of drystripping boron-carbon films using oxygen-containing oxidizing agents incombination with hydrogen-containing reducing agents. In one embodiment,alternating plasmas of hydrogen and oxygen are used to remove aboron-carbon film. In another embodiment, co-flowed oxygen and hydrogenplasma is used to remove a boron-carbon containing film. A nitrous oxideplasma may be used in addition to or as an alternative to either of theabove oxygen plasmas. In another embodiment, a plasma generated fromwater vapor is used to remove a boron-carbon film. The boron-carbonremoval processes may also include an optional polymer removal processprior to removal of the boron-carbon films. The polymer removal processincludes exposing the boron-carbon film to a plasma formed from anoxygen-containing gas, a fluorine-containing gas, or a combinationthereof to remove from the surface of the boron-carbon film anycarbon-based polymers generated during a substrate etching process.

In one embodiment, a method for stripping a film from a substratecomprises positioning a substrate having a film thereon in a chamber,wherein the film includes at least one of boron or carbon. The film isthen exposed to oxygen ions or radicals and hydrogen ions or radicals togenerate one or more volatile compounds, and the one or more volatilecompounds are exhausted from the chamber.

In another embodiment, a method for stripping a boron-carbon film from asubstrate positioned in a chamber comprises exposing a substratecomprising boron and carbon to a plasma containing oxygen radicals orions and hydrogen radicals or ions. The hydrogen radicals or ions arereacted with the boron to form a volatile boron species, and the oxygenradicals or ions are reacted with the carbon to form a volatile carbonspecies. The volatile boron species and the volatile carbon species arethen removed from the chamber.

In another embodiment, a method for stripping a film from a substratepositioned in a chamber comprises exposing a substrate to a plasmaformed from a compound comprising H_(x)O_(y), where x and y are integersor non-integers greater than 1. The film is then contacted with theplasma to form one or more volatile species, and the volatile speciesare removed from the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a flow diagram illustrating a method of removing aboron-carbon film using alternating hydrogen and oxygen plasmasaccording to one embodiment of the invention.

FIG. 2 is a flow diagram illustrating a method of removing aboron-carbon film using a plasma containing both oxygen and hydrogenaccording to one embodiment of the invention.

FIGS. 3A and 3B illustrate the effect of chamber pressure and RF poweron etch rate when using a plasma containing oxygen and hydrogen.

FIG. 4 is a flow diagram illustrating a method of removing aboron-carbon film using plasma generated from hydrogen and nitrous oxideaccording to one embodiment of the invention.

FIG. 5 is a flow diagram illustrating a method of removing aboron-carbon film using plasma generated from water vapor according toone embodiment of the invention.

FIG. 6 illustrates the etching selectivity of water vapor plasma.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments of the invention generally relate to methods of drystripping boron-carbon films using oxygen-containing oxidizing agents incombination with hydrogen-containing reducing agents. In one embodiment,alternating plasmas of hydrogen and oxygen are used to remove aboron-carbon film. In another embodiment, co-flowed oxygen and hydrogenplasma is used to remove a boron-carbon containing film. A nitrous oxideplasma may be used in addition to or as an alternative to either of theabove oxygen plasmas. In another embodiment, a plasma generated fromwater vapor is used to remove a boron-carbon film. The boron-carbonremoval processes may also include an optional polymer removal processprior to removal of the boron-carbon films. The polymer removal processincludes exposing the boron-carbon film to a plasma formed from anoxygen-containing gas, a fluorine-containing gas, or a combinationthereof to remove from the surface of the boron-carbon film anycarbon-based polymers generated during a substrate etching process.

Embodiments of the invention may be practiced in the Producer® SE orProducer® GT chambers available from Applied Materials, Inc., of SantaClara, Calif. It is contemplated that other chambers, including thoseproduced by other manufacturers, may benefit from embodiments describedherein.

FIG. 1 is a flow diagram 100 illustrating a method of removing aboron-carbon film using alternating hydrogen and oxygen plasmasaccording to one embodiment of the invention. Flow diagram 100 begins atoperation 102, in which a substrate having a boron-carbon film thereon,such as a boron-carbon hardmask, is positioned on a substrate supportwithin a stripping chamber. The substrate and the boron-carbon filmthereon are heated to a temperature less than about 750° C., such asabout 200° C. to about 400° C. The boron-carbon film may be aboron-doped carbon, or a hydrogenated boron carbide having an atomicratio of boron to carbide of about 2:1 or less. The substrate isgenerally a silicon-containing substrate, such as a 300 millimetersilicon wafer, and may have one or more dielectric or conductive metallayers disposed thereon. For example, the substrate may have a silicondioxide layer disposed thereon, over which the boron-carbon layer isdisposed to act as an etching hardmask during a previously performedetching of the silicon dioxide layer. It is contemplated that substratesother than silicon-containing substrates may be used.

After positioning the substrate on a support, carbon-based polymerslocated on the boron-carbon film are optionally removed in a polymerremoval operation 104. The carbon-based polymers are generated on theupper surface of the boron-carbon layer during a previously performedetching process in which the boron-carbon layer acts as an etchinghardmask. During the etching, the substrate and the boron-carbon layerthereon are exposed to an etchant, such as C₄F₈, to etch a desiredpattern into the substrate. Due to polymerization of carbon andfluorine, the etching process produces a carbon-based polymer, which mayalso include silicon and/or oxygen. The carbon-based polymer isgenerally removed prior to the stripping process to remove highermolecular weight molecules to allow for more efficient stripping of theboron-carbon film.

The carbon-based polymer is removed from the surface of the boron-carbonfilm by exposing the carbon-based polymer to a plasma formed from afluorine-containing gas, an oxygen-containing gas, or a combinationthereof. For example, the carbon-based polymer may be removed using aplasma formed from oxygen gas and NF₃ having a ratio of about 100:1.Generally, the amount of fluorine desired in the plasma increases withthe amount of silicon present in the carbon-based polymer. Sinceoxygen-containing plasmas are capable of removing the carbon-basedpolymer, especially when the carbon-based polymer contains relativelylow amounts of silicon, operation 104 can be omitted due to the exposureof the substrate to an oxygen-containing plasma in operation 106(discussed below).

During the polymer removal process, a remotely generated plasma usingoxygen gas and NF₃ gas is provided to the stripping chamber at a flowrate of about 1 SCCM to about 15,000 SCCM per 300 millimeter substrate,for example, about 100 SCCM to about 5,000 SCCM. The ratio of oxygen toNF₃ is about 100:1 to about 1000:1. The pressure within the strippingchamber is maintained at a pressure within a range from about 1millitorr to about 760 Torr, such as about 4 millitorr to about 10 Torr,while the substrate is maintained at a temperature less than 750° C. Theoxygen and the NF₃ react with the carbon-based polymer to form avolatile compound which is then exhausted from the stripping chamber.Under such conditions, the carbon-based polymer is removed at a rate ofabout 2,000 angstroms per minute to about 10,000 angstroms per minute.It is contemplated that the carbon-based polymer may be over-etched toensure removal from the surface of the substrate.

After removal of the carbon-based polymer layer from the boron-carbonlayer, the boron-carbon layer is stripped from the surface of thesubstrate in operation 106. Operation 106 includes two sub-operations,106A and 106B. In sub-operation 106A, the boron-carbon layer is exposedto an ionized oxygen-containing compound, such as oxygen plasma, andthen subsequently, in sub-operation 106B, the substrate is exposed to anionized hydrogen-containing compound, such as hydrogen plasma. Insub-operation 106A, the oxygen ions react with the carbon of theboron-carbon film to form a volatile compound (e.g., CO₂) which isexhausted from the chamber. After about 10 seconds to about 50 secondsof exposure to the ionized oxygen, the boron-carbon film forms arelatively higher concentration of boron near the surface of the filmdue to the removal of carbon. The removal rate of the boron-carbon filmbegins to decrease due to the reduction of available carbon on thesurface of the film. At this point, the flow rate of theoxygen-containing compound to the stripping chamber is halted, and theremaining oxygen-containing compound is exhausted from the strippingchamber.

In sub-operation 106B, the boron-carbon layer is exposed to ahydrogen-containing compound plasma which reacts with the boron in theboron-carbon layer to form a volatile compound (e.g., B₂H₆) which isthen exhausted from the chamber. The boron-carbon layer is exposed tothe hydrogen plasma for about 10 seconds to about 50 seconds, until theboron-carbon film has a relatively higher concentration of carbon nearthe surface of the boron-carbon film. After a predetermined time, theflow of hydrogen gas is halted, and sub-operation 106A is then repeated.Operation 106, which includes sub-operations 106A and 106B, may berepeated a desired amount of times in order to sufficiently remove theboron-carbon film from the substrate surface.

Each of the hydrogen-containing compound and the oxygen-containingcompound are provided to the stripping chamber at flow rate of about 5SCCM to about 15,000 SCCM per 300 millimeter substrate. For example, thehydrogen gas and the oxygen gas may be provided to the stripping chamberat a flow rate of about 500 SCCM to about 10,000 SCCM and about 250 SCCMto about 5000 SCCM, respectively. The hydrogen-containing compound andthe oxygen-containing compound are ionized using an RF generatoroperating at 13.56 MHz which applies about 100 watts to about 3,000watts of power, for example, about 1,000 watts to about 3,000 watts. Thepressure within the stripping chamber is maintained at a pressure withina range from about 1 millitorr to about 760 Torr, such as about 50millitorr to about 10 Torr, or about 5 Torr to about 100 Torr.

It is to be noted that since the oxygen-containing compound reacts withcarbon, and the hydrogen-containing compound reacts with boron, theexposure times of each compound can be tailored based on the atomiccomposition of the boron-carbon film to effect a desired removal rate.For example, if the boron concentration in the boron-carbon film isabout twice the concentration of the carbon in the film, then thehydrogen exposure time may be greater than the oxygen exposure time,such as about two times greater (assuming both plasmas have about thesame etch rate).

Flow diagram 100 illustrates one embodiment for removing a boron-carbonfilm; however, other embodiments are also contemplated. In oneembodiment, operations 102, 104, and 106 are all performed in the samechamber. In another embodiment, it is contemplated that operation 104may occur in a separate chamber, such as an etching chamber, and mayoccur before positioning the substrate in a stripping chamber. Inanother embodiment, it is contemplated that the plasma of operation 104can be a capacitively coupled or inductively coupled in addition to oras an alternative to a remotely generated. For example, it iscontemplated that a capacitively coupled plasma may be generated from afluorine-containing gas and an oxygen-containing gas. Alternatively, acapacitively coupled plasma may be generated from water vapor and aninert gas. In such an embodiment, water vapor may be introduced to thechamber at a flow rate between about 10 SCCM and 10,000 SCCM, such asabout 4,000 SCCM. The inert gas may be provided to the chamber at a flowrate of about 3,000 SCCM.

In another embodiment, it is contemplated that other fluorine-containinggases can be used in operation 104. For example, it is contemplated thatCF₄, C₃F₆, CHF₃, CH₂F₂, and CH₃F may be utilized. In another embodiment,it is contemplated that the NF₃ plasma of operation 104 or theoxygen-containing or hydrogen-containing plasmas of operation 106 can begenerated in situ via inductive coupling or may be remotely generated.In yet another embodiment, it is contemplated that the oxygen-containingcompound and hydrogen-containing compound of operation 106 may becarried to the stripping chamber using a carrier gas, such as argon,helium or nitrogen. The carrier gases may be provided to the strippingchamber containing a 300 millimeter substrate at a flow rate of about 5SCCM to about 15,000 SCCM. In another embodiment, it is contemplatedthat the chamber may be flushed between sub-operations 106A and 106Busing a carrier gas to avoid reaction between the hydrogen and theoxygen. In yet another embodiment, it is contemplated that sub-operation106B may be performed prior to sub-operation 106A.

In another embodiment, it is contemplated that any compound whichprovides oxygen, such as O₂, N₂O, CO₂, NO, or NO₂, may be used inoperation 106. Additionally, it is also contemplated that otherhydrogen-containing compounds may be used in addition to or asalternatives to hydrogen gas in operation 106. For example, it iscontemplated that ammonia may be used in addition to or as analternative to hydrogen gas.

In one example, a boron-carbon film having a thickness of about 2000angstroms is exposed to 1500 SCCM of hydrogen plasma for 30 seconds at achamber pressure of 7 Torr and substrate temperature of 400° C. Theboron-carbon film is then exposed to 1500 SCCM of oxygen plasma for 30seconds at a chamber pressure of 7 Torr and substrate temperature of400° C. The boron-carbon film is further exposed to alternating hydrogenand oxygen plasmas until the film is removed. The boron-carbon film wasremoved in about 20 minutes.

FIG. 2 is a flow diagram 200 illustrating a method of removing aboron-carbon film using a plasma containing both oxygen and hydrogenaccording to one embodiment of the invention. Flow diagram 200 includesoperations 102, 104, and 206. Operations 102 and 104 are similar tooperations 102 and 104 described with reference to flow diagram 100.After positioning a substrate on a support in operation 102, andremoving the carbon-based polymer in operation 104, the substrate andthe boron-carbon film thereon are exposed to a plasma or ionized gasformed from a hydrogen-containing compound, such as diatomic hydrogen,and an oxygen-containing compound, such as diatomic oxygen, in operation206. Thus, while operation 106 of flow diagram 100 exposes theboron-carbon film to a cycle alternating hydrogen-containing andoxygen-containing plasmas, operation 206 exposes the boron-carbon filmto simultaneous hydrogen-containing and oxygen-containing plasmas.

In operation 206, the hydrogen-containing compound and oxygen-containingcompound are provided to the stripping chamber at flow rate of about 5SCCM to about 15,000 SCCM per 300 millimeter substrate to remove aboron-carbon layer from the surface of the substrate. For example, thehydrogen-containing compound and the oxygen-containing compound may beprovided at a flow rate of about 200 SCCM to about 4,000 SCCM. Thehydrogen-containing compound and the oxygen-containing compound areionized using an RF generator operating at 13.56 MHz and applying about100 watts to about 3,000 watts of power, such as about 1,500 watts toabout 2,000 watts of power. The substrate is maintained at a temperatureless than 750° C., such as at about 400° C. The pressure within thestripping chamber is generally maintained at a pressure less than about20 Torr, such as about 7 Torr to about 19 Torr. By maintaining thechamber pressure at less than about 20 Torr, the probability of oxygenplasma and hydrogen plasma undesirably and dangerously reacting withinthe stripping chamber is greatly reduced.

The hydrogen-containing plasma and the oxygen-containing plasma withinthe chamber contact the boron-carbon film and react to form volatilecompounds which are then exhausted from the chamber. Since the oxygengenerally forms a volatile compound with the carbon in the boron-carbonfilm, and the hydrogen forms a volatile compound with the boron, it iscontemplated that the relative ratio of oxygen to hydrogen (and/or flowrates of oxygen and hydrogen) can be adjusted depending on thecomposition of the boron-carbon film to effect the desired removal rate.Table 1 illustrates the change in removal rate of a boron-carbon filmfrom the surface of a 300 millimeter substrate using varied processparameters.

TABLE 1 H₂ O₂ Etch P Power Flow rate Flow rate rate (Torr) (watts) T (°C.) (SCCM) (SCCM) (Å/min) Example 1 19 1500 400 1000 500 140 Example 219 1900 400 1000 500 155 Example 3 19 1900 400 1500 750 152 Example 4 191900 400 700 350 151 Example 5 19 1900 400 400 200 141 Example 6 19 1900400 1250 250 116 Example 7 19 1900 400 750 750 102 Example 8 19 1900 400250 1250 119 Example 9 19 1900 400 300 300 104 Example 10 19 1900 400200 400 101 Example 11 19 1500 400 400 200 149 Example 12 19 1500 400500 1000 88 Example 13 9 1500 400 1000 500 107

With respect to increased oxygen or hydrogen flow rates, excess oxygenor hydrogen in the plasma generally has little effect on etching rate.The rate of etching is limited by the amount of boron or carbon presenton the surface of the boron-carbon film with which the oxygen orhydrogen can form a volatile compound, and generally is notsignificantly increased with the inclusion of excess process gas.However, it should be noted that the etching rate can be increasedthrough the inclusion of additional process gas when the process gas isthe limiting reactant (e.g., excess reactant sites are present on thesurface of the boron-carbon film).

Flow diagram 200 illustrates one embodiment of stripping a boron-carbonfilm; however, other embodiments are also contemplated. In anotherembodiment, it is contemplated that the oxygen-containing compound andhydrogen-containing compound in operation 206 may be introduced to thestripping chamber using a carrier gas, such as argon, helium, ornitrogen, having a flow rate less than 15,000 SCCM per 300 millimetersubstrate. The inclusion of carrier gas to the processing volume maydecrease the rate at which the boron-carbon film is etched, but may alsoincrease plasma uniformity and stability.

FIGS. 3A and 3B illustrate the effect of chamber pressure and RF poweron etch rate when using a plasma containing oxygen and hydrogen. In FIG.3A, a boron-carbon film at 400° C. was removed from a substrate using aplasma formed from 2,000 SCCM of hydrogen gas and 1,000 SCCM of oxygengas at 1,000 watts of RF power. As the pressure within the chamber isincreased, the etching rate of the boron-carbon film is correspondinglyincreased. Thus, in all methods described herein, etch rate of theboron-carbon film may be controlled by adjusting the pressure within thechamber. In FIG. 3B, a boron-carbon film at 400° C. was removed usingplasma formed from 2,000 SCCM of hydrogen gas and 1,000 SCCM of oxygengas. The chamber pressure was maintained at 9 Torr. As the RF powerapplied to the plasma is increased, the etching rate of the boron-carbonfilm is correspondingly increased.

FIG. 4 is a flow diagram illustrating a method of removing aboron-carbon film using plasma generated from hydrogen and nitrous oxideaccording to one embodiment of the invention. Flow diagram 400 includesoperations 102, 104, and 406. Operations 102 and 104 are similar tooperations 102 and 104 described with reference to flow diagram 100.After positioning a substrate on a support in operation 102, andremoving the carbon-based polymer in operation 104, the substrate andthe boron-carbon film thereon are exposed to a plasma formed fromhydrogen and nitrous oxide in operation 406. Thus, while flow diagram200 uses oxygen as an oxidizing agent to remove carbon from theboron-carbon film, flow diagram 400 uses nitrous oxide as an oxidizingagent. The use of nitrous oxide as an oxidizing agent allows thepressure within the chamber to be increased, thus increasing etch rate,while reducing the probability of undesired reactions occurring withinthe processing environment as is likely when using oxygen as anoxidizing agent.

In operation 406, hydrogen gas and nitrous oxide gas are provided to thestripping chamber at flow rate of about 5 SCCM to about 15,000 SCCM fora 300 millimeter substrate to remove a boron-carbon layer from thesurface of the substrate. For example, the hydrogen gas and the nitrousoxide gas may each be provided at a flow rate of about 200 SCCM to about4,000 SCCM. The hydrogen gas and the nitrous oxide gas are ionized usingan RF generator operating at 13.56 MHz and applying about 100 watts toabout 3,000 watts of power, such as about 1,500 watts to about 2,000watts of power. The substrate is maintained at a heater temperature lessthan 750° C., such as at about 400° C. The pressure within the strippingchamber is maintained at less than 760 Torr, such as about 40 Torr toabout 60 Torr. The nitrous oxide plasma and the hydrogen plasma reactwith the boron-carbon film to form volatile compounds which are thenexhausted from the chamber.

Table 2 illustrates some exemplary process recipes for removing aboron-carbon film from the surface of a 300 millimeter substrate using aplasma formed from hydrogen and nitrous oxide.

TABLE 2 H₂ N₂O Etch P Power Flow rate Flow rate rate (Torr) (watts) T (°C.) (SCCM) (SCCM) (Å/min) Example 14 49 1500 400 1500 750 104 Example 1549 1500 400 1000 500 121 Example 16 49 1500 400 500 250 143 Example 1749 1500 400 250 125 129 Example 18 60 2000 400 1500 1000 190 Example 1960 2000 400 1125 750 215 Example 20 60 2000 400 750 500 239 Example 2160 2000 400 375 250 244 Example 22 60 2000 400 225 150 241

As illustrated in Table 2, the use of nitrous oxide as an oxidizingagent generally yields a greater etching rate than when using oxygen asan oxidizing agent. This is due partly to the higher chamber pressureswhich can be utilized when using nitrous oxide. In another embodiment,it is contemplated that the oxidizing gas may be a mixture of nitrousoxide and oxygen, in which case, the pressure in the chamber may bepermitted to exceed 20 Torr. Furthermore, although flow diagram 400 isdescribed with reference to co-flowing nitrous oxide and hydrogen gas,it is contemplated that the nitrous oxide and hydrogen gas beindependently provided to the chamber in a cyclical manner. In yetanother embodiment, it is contemplated that carbon dioxide may be usedin addition to or as an alternative to nitrous oxide.

FIG. 5 is a flow diagram 500 illustrating a method of removing aboron-carbon film using plasma generated from water vapor according toone embodiment of the invention. Flow diagram 500 includes operations102, 104, and 506. Operations 102 and 104 are similar to operations 102and 104 described with reference to flow diagram 100. After positioninga substrate on a support in operation 102, and removing the carbon-basedpolymer in operation 104, the substrate and the boron-carbon filmthereon are exposed to a plasma formed from water vapor in operation506.

In operation 506, water vapor is produced by a water vapor generator(WVG) and is provided to a stripping chamber where the water vapor isignited into a plasma to etch a boron-carbon film from the surface of asubstrate. The water vapor is introduced to the stripping chamber at aflow rate of about 5 SCCM to about 15,000 SCCM per 300 millimetersubstrate. The substrate is maintained at a temperature less than about750° C., such as about 300° C. to about 500° C., for example about 400°C., while the pressure in the chamber is maintained at less than about760 Torr, such as about 10 Torr to about 760 Torr, such as about 10 Torrto about 100 Torr, for example about 65 Torr. RF power within a range ofabout 10 watts to 3,000 watts, for example about 2,700 watts, is appliedto the water vapor to generate a plasma containing oxygen, hydrogen, andhydroxyl ions or radicals, which react with the boron-carbon film toform volatile compounds which are exhausted from the chamber.

Flow diagram 500 illustrates one embodiment for stripping a boron-carbonfilm; however, additional embodiments are also contemplated. Forexample, it is contemplated that the water vapor may be generated via insitu steam generation. In another embodiment, it is contemplated thatnon-stoichiometric combinations of oxygen and hydrogen (e.g.,H_(x)O_(y), where x and y may be integers or non-integers both greaterthan zero) may be input to or generated by the WVG. In such anembodiment, some hydrogen peroxide may be generated by the water vaporgenerator. In another embodiment, it is contemplated that oxygen gas,helium gas, nitrogen gas, argon gas, nitrous oxide gas, and or/hydrogengas may be provided to the stripping chamber in addition to water vapor.In such an embodiment, the addition of hydrogen has been found toincrease the removal rate of the boron-carbon film, especially inboron-carbon films containing a higher concentration of boron ascompared to carbon. The addition of other carrier gases, such as helium,has been observed to lower the rate of removal of the boron-carbon film,while simultaneously improving etch uniformity. In another embodiment,it is contemplated that the water vapor may be used to strip a carbonfilm, such as amorphous carbon, containing substantially no boron.Alternatively, it is contemplated that the water vapor may be used tostrip a boron film, such as amorphous boron, containing substantially nocarbon.

In another embodiment, it is contemplated that a fluorine-containing gasor a chlorine-containing gas may be ionized in operation 506 incombination with the water vapor to increase the etching rate of theboron-carbon film. In such an embodiment, operation 104 may be omitted.The fluorine-containing gas or the chlorine-containing gas is generallyprovided to the chamber at a flow rate between about 10 SCCM and 50SCCM. In order to avoid undesirably etching dielectric materials presenton the substrate, the flow rate of the fluorine-containing gas or thechlorine-containing gas is tapered, reduced, or eliminated whenapproaching the end of operation 506. It is believed that reduction inflow rate near the end of operation 106 does not undesirably etchexposed dielectric materials due to the mechanism in which thefluorine-containing gas or the chlorine-containing gas assists inremoval of the boron-carbon layer.

Generally, dielectric material on the substrate is exposed in vias ortrenches formed into the substrate during a previous etching process,while boron-carbon material is exposed on the upper surface of thesubstrate. Thus, the fluorine-containing gas or the chlorine-containinggas which enters the chamber and is ignited into a plasma generallycontacts and reacts with the boron-carbon layer prior to contacting thedielectric material in the vias or trenches. However, as theboron-carbon film is removed, the probability of the fluorine-containinggas or the chlorine-containing gas contacting and undesirably removingthe dielectric material is increased. Therefore, the flow rate of thefluorine-containing gas or the chlorine-containing gas is reduced as thethickness of the boron-containing layer decreases in order to reduce theprobability of etching the dielectric material.

In another embodiment, when generating a capacitively coupled watervapor plasma, the spacing between the substrate and a face place locatedwithin the chamber may be within a range of about 20 mils to about 600mils, for example about 170 mils. Reduced spacing between the substrateis beneficial when processing substrates in larger volumes (for example,when processing large area substrates) under higher pressures (forexample, greater than about 7 Torr). When processing substrates atpressures greater than about 7 Torr, the reduced spacing facilitatesplasma sustainability. In one example, when processing a substrate atabout 30 Torr, the spacing between the substrate and the face plate maybe about 300 mils. At 40 Torr, the spacing between the substrate and theface plate may be within a range of about 240 mils to about 270 mils. Ata pressure of about 50 Torr, the spacing between the substrate and theface plate may be less than 200 mils. At a pressure above 50 Torr, forexample about 65 Torr, the spacing may be about 170 mils. Performing astripping operation as described herein above a pressure of 50 Torrresults in

Table 3 illustrates a change in etch rate of a boron-carbon film inresponse to a change in process gas flow rate. Each of Examples 23-30 inTable 3 includes at least 500 SCCM of helium gas as a carrier gas toincrease etch uniformity, and may contain additional carrier gas, asnoted in Table 3.

TABLE 3 Power H₂O Flow He Flow Carrier Etch rate P (Torr) (watts) T (°C.) rate (SCCM) rate (SCCM) gas (SCCM) (Å/min) Example 23 50 1900 4001000 250 0 679 Example 24 50 1900 400 1000 400 0 613 Example 25 50 1900400 1000 250 150 H₂ 720 Example 26 50 1900 400 1000 250 350 H₂ 630Example 27 50 1900 400 1000 250 150 Ar 617 Example 28 50 1900 400 1000250 350 Ar 527 Example 29 50 1900 400 1000 250 750 Ar 389 Example 30 501900 400 1000 500 0 546

As shown in Table 3, Example 29, which contains the highest total flowrate of carrier gas (250 SCCM of helium and 750 SCCM of argon) has thelowest etch rate.

Table 4 includes some examples of boron-carbon film stripping recipes athigher severity. High severity conditions include pressures above 50Torr, high gas flow rates of at least 7 sLm, and higher power input ofat least about 2000 watts. Such high severity conditions can maintain awater vapor plasma, optionally with excess hydrogen, at a spacing lessthan 200 mils.

TABLE 4 H₂O Flow He Flow Hydrogen Power Spacing rate rate Flow Rate P(Torr) (watts) (mils) T (° C.) (mgm) (SCCM) (mgm) Example 31 65 2700 170400 5400 2400 0 Example 32 65 2700 170 400 5400 2400 30 Example 33 652700 170 400 5400 2400 600As noted above, it is thought that adding hydrogen in excess of thestoichiometric proportions of water may accelerate reactions with boronand accelerate the overall rate of removal of boron-carbon films. Theexact amount of excess hydrogen that is most beneficial depends on theamount of boron in the carbon film.

FIG. 6 illustrates the etching selectivity of water vapor plasma. PlasmaA includes 1,000 SCCM of water vapor and 500 SCCM of helium generatedinto a plasma using 1900 watts of RF power. The stripping chamber ismaintained at 50 Torr, and the substrate is maintained at 400° C. PlasmaA etched the boron-carbon film at a rate of about 570 angstroms perminute, and did not etch silicon oxide, silicon nitride, or amorphoussilicon.

Plasma B includes 1,000 SCCM of water vapor, 250 SCCM of helium, and 150SCCM of hydrogen generated into a plasma using 1900 watts of RF power.The stripping chamber is maintained at 50 Torr, and the substrate ismaintained at 400° C. Plasma B etched the boron-carbon film at a rate ofabout 770 angstroms per minute, and did not etch silicon oxide, siliconnitride, or amorphous silicon.

Benefits of the methods described herein include stripping boron-carbonfilms without damaging dielectric materials or underlying metal layerslocated on a substrate. The stripping methods allow for etching rate, aswell as etching uniformity to be controlled by varying plasmacomposition.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for stripping a film from a substrate, comprising:positioning a substrate having a film thereon in a chamber, the filmcomprising boron and carbon; exposing the film to a water vapor plasmaat a pressure above 50 Torr to generate one or more volatile compoundsfrom the boron and carbon; and exhausting the one or more volatilecompounds from the chamber.
 2. The method of claim 1, wherein an atomicratio of boron to carbon in the film is within a range of about 1:1 toabout 3:1.
 3. The method of claim 1, wherein the water vapor plasma isformed from a precursor gas comprising water vapor and a carrier gas,and a flow rate of the precursor gas is at least about 7 sLm.
 4. Themethod of claim 2, wherein the plasma is maintained at a power input ofat least 2,000 watts and spacing less than 200 mils.
 5. The method ofclaim 4, wherein the water vapor plasma comprises excess hydrogen.
 6. Amethod of removing a boron-carbon film, comprising: exposing theboron-carbon film to a water vapor plasma containing excess hydrogen ina processing chamber; maintaining a pressure in the processing chamberabove 50 Torr; reacting oxygen in the water vapor plasma with carbon inthe boron-carbon film to form volatile carbon species; reacting hydrogenin the water vapor plasma with boron in the boron-carbon film to formvolatile boron species; and removing the volatile carbon species and thevolatile boron species from the processing chamber.
 7. The method ofclaim 6, wherein the water vapor plasma is formed from a precursor gascomprising the excess hydrogen, and the precursor gas is provided to theprocessing chamber at a flow rate of at least 7 sLm.
 8. The method ofclaim 7, wherein the water vapor plasma is formed by applying at least2,000 watts of power to the precursor gas.